Geometric instrument



Aug. 16, 1966 F. P. WILHELM 3,

GEOMETRI C INSTRUMENT Filed July 24, 1964 2 Sheets-Shea; 2

45 6 n W 9 '1 l; )a C 39 Eig. 5

FRED P. WIILHELM ATTORNEY 28 I NVENTOR.

United States Patent 3,266,153 GEOMETRIC INSTRUMENT Fred P. Wilhelm, 23943 Grunalt, Warren, Mich. Filed July 24, 1964, Ser. No. 384,826 8 Claims. (Cl. 33--77) This invention relates to geometric instruments, and more particularly to a device for plotting views of three dimensional bodies, particularly but not exclusively, with curvilinear elements.

In designing various constructions, or parts thereof, of such a nature it is often desired for a number of reasons to make in addition to three standard views, the front view, the top view, and the end view, additional views with the object turned at a certain angle, giving a view having some particular advantage for the purposes intended, such as designing dies in cases of sheet metal articles, and the like.

Producing such views has heretofore been done by graphical methods, and such operations require not only a thorough knowledge of the principles of descriptive geometry and application thereof to the problem at hand, but also providing three views of the object and thereupon providing the desired view on the basis of such three views by plotting the points at the intersection of two lines extended to the third plane. Such work, in addition to requiring exceedingly elaborate layouts, provides possibilities of mistakes, and produces erroneous results which may be carried on without detection throughout the entire designing stage and be discovered only when dies or other tools for the erroneously shown parts are being made. Often, the results of such mistakes are very costly. Graphical operations of this nature are particularly complicated, and time consuming should the object involve curvilinear elements, such as curved edges and the like. This results from the fact that while projecting straight lines can be done by projecting their terminal points and connecting the same by a straight line, in cases of curvilinear lines, such projections must be produced point by-point, with the number of intermediate points being sufliciently large to insure production of smooth and correct projections.

Accordingly, the drafting and designing work including such operations, requires highly skilled and expensive personnel, not only in plotting such drawings and designing but also in checking the same. In addition to the high expense, considerable delays are often encountered under such conditions.

One of the objects of the present invention is to provide an improved plotting device whereby the dimensions of various projected lines, determining the outline of the object in the special projections are determined not by measuring distances in the projections on the auxiliary planes, but are produced analytically with the aid of the device itself, and plotted thereby directly without the necessity of measuring such distances on the scale and thereupon transferring them on the drawing.

A further object of the present invention is to provide an improved plotting device particularly, but not exclusively for plotting curvilinear outlines in special positions, whereby positions of various points of a curve in a special projection are determined not by intersection of two lines projected from other views but by laying off, with the aid of the device, a point on a straight line produced by moving a pointer thereof along a straight deviceproduced line, with said distance being also determined by the device itself.

A further object of the present invention is to provide a device of the foregoing nature which can be alined on the drawing in a plurality of positions for movement of its t followers along parallel lines, such alinement being at- 'ice tained with a T-Square head attached to the device, or by attaching to the device a cross bar moved on rollers along a rail provided on the top of a drawing board.

A still further object of the present invention is to provide an improved device of this general nature in which the desired relationship of the distances to be laid off to the distances in one of the straight projections is determined by the gear ratio of the gear train carried by the device.

A still further object of the present invention is to provide a device of the nature specified in the preceding paragraph in which changing such gear ratios can be easily effected by interchanging gears.

A still further object of the present invention is to provide a device of the foregoing nature, having two followers positively actuating a single pointer through a driving train of mechanical elements, such as toothed connectors.

A still further object of the present invention is to provide an improved device of the foregoing nature in which the followers are interconnected by differential devices, thus permitting simultaneous movements of both followers.

A still further object of the present invention is to pro vide an improved method of making layouts, and particularly views of special plane vprojections, in accordance with which location of the points of curved elements on the special planes by projecting to intersection of two lines is eliminated, and in which such location is found by laying off a distance along a straight line on said projected view.

It is an added object of the present invention to provide an improved device of the foregoing nature which is relatively simple in construction, is dependable in operation, is relatively easy to use, and is relatively inexpensive to manufacture and repair.

Further objects and advantages of this invention will be apparent from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification, wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is an elevational view of a portion of a vertical drawing board with my improved device operatively mounted thereon.

FIG. 2 is a fragmentary and diagrammatic elevational view showing a portion of the gear connection between the near follower rack and the pointer rack.

FIG. 3 is a fragmentary and diagrammatic elevational view showing -a portion of the gear connection between the far follower rack and the pointer rack.

FIG. 4 is a sectional view taken in the direction of the arrows on the section plane passed through the section line 44 of FIG. 1.

FIG. 5 is a sectional view taken in the direction of the arrows on the section plane passed through thesection line 5-5 of FIG. 1, and showing the driving connection from the lower follower rack to the pointer rack.

FIG. 6 is a sectional view taken in the direction of the arrows on the section plane passed through the section line 66 ofFIG. 1. T

FIG. 7 is a fragmentary sectional view taken in the direction of the arrows on the section plane passed through the section line 77 of FIG. ,1.

FIG. 8 is a sectional view similar in part to FIG. 5 but showing the driving connection from the upper follower rack and the pointer r-a-ck.

FIG. 9 is a top view of the lower follower.

It is to be understoodthat the invention. is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodita ments and of being practiced or carried out in various ways within the scope of the claims. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

In the drawings there is shown, by way of example, an improved projecting and plotting device embodying the invention. Referring specifically to the drawings, 'my improved device generally designated by the numeral is illustrated therein as used in connection with a vertically extending drawing board 11. The device is operatively mounted on said drawing board to be moved along the same, preserving a constant angular relationship therewith, in the illustrated embodiment the perpendicular relationship with the base line of the drawing. Such mounting is attained by providing along the upper edge of the board a rail 12 forming a-track for rollers 13 se- 4 cured to the head bar 14, which bar is, in turn, secured to the frame member of the device, perpendicularly thereto. An angular brace 16 has its ends secured to the head bar 14 and the frame member 20, respectively, to impart requisite rigidity to the construction. It will be clear now that as the device is moved along the board, a base line 17 may be drawn along the bottom of the drawing by a pencil or other marking instrument placed through the hole of a marker 15, and any point on the device moves along a line parallel to said base line.

The frame member 20 of the device is in the form of a channel, the inner side surfaces 18 and 19 thereof are parallel to each other. The channel frame member 20 may be of a solid construction, or a built-up construction, as shown. In the operative position of the device said surfaces are perpendicular to the track of the rail 12 and therefore to the base line 17.

Within the frame member 20, ie, in the hollow of the channel thereof, there are mounted a lower follower rack and an upper follower rack 26, having their smooth back surfaces bearing on the guiding surface 18 of the channel and their teeth pointing inwardly of the channel. To the lower rack 25 there is secured, for movements therewith, a lower follower generally designated by the numeral 27, see FIG. 7, carrying a transparent piece 28 provided with a locating hole 29. To

the upper follower rack 26 there is secured for movements therewith a follower of a construction similar to that of the follower 27, and having a locating hole 31. The distance L from the surface 18 to the center of the locating hole 29 of the follower 27, and the distance M from said surface 18 to the locating hole 3 1 of the follower 30 are equal. Therefore, with the frame member 20 being stationary, as the racks 25 and 26 and the followers 27 and 30 are moved up and down, the centers of the locating holes 29 and 31 thereof move along the same straight line perpendicular to the base line 17.

On the other side of the hollow of the channel frame member 20 there is mounted a pointer rack 35 having its smooth back surface in contact with the guiding surface 19, and its teeth pointing inwardly of the channel. To said rack 35 there is secured for movements therewith a pointer 36 bridging with its upper portion 37 over the channel frame member 20, see FIG. 4, and provided on the other side of the member 20 with a construction similar to that of the followers 27 and 30, and with the end thereof carrying a transparent plastic piece 38 provided with a marking hole 39. By virtue of such a construction, movements of the rack 35 produce movements of the center of the marking hole 39 along lines parallel to the line of movements of the centers of the locating holes 29 and 31 of the followers 27 and 39. It is desirable but not necessary that the center of the marking hole 39 also moves along the same straight line as the centers of the holes 29 and 31 of the followers.

The channel frame member 20 is provided with a cover 4!, 40. In said cover there is provided a slot 41 running adjacent to and parallel to the guiding surface 18 for the passage therethrough of the connecting bars 42 and 43 of the followers 27 and 30, respectively. A second slot 44 is provided in the cover on the other side of the members 2t), adjacently to and parallel to the guiding surface 19, for passage of the connecting bar 45 with the aid of which the pointer 36 is connected with the rack 35. Since the followers 27 and 30 operate over the lower portion of the drawing, the followers slot 41 is provided in the lower portion of the cover 40, see FIG. 1. Similarly, since the pointer 36 operates in the upper portion of the drawing, the pointer slot 44.is provided only in the upper portion of the cover 40.

In accordance with the invention there are provided separate driving connections between each of the follower racks 25 and 26 and the pointer rack 35. One of these connections, in the present embodiment the connection between the lower follower rack 25 and the pointer rack 35, includes the gear train producing movements of the rack 35 and of the pointer 36 in response to the movements of the rack 25 and the followed 27 in the ratio equal to the sine of a certain angle. On the other hand, the other driving connection, in the present embodiment the driving connection between the upper follower rack 26 and the pointer rack 35 includes a gear train having a ratio producing in response to the movements of the follower 30 and its rack 26 movements in the ratio equal to the cosine of the same angle.

The angle in question is the angle through which the object is turned to produce a special projection. Such an angle may also be thought of as the angle through which the projection plane is turned to produce such projection. Thus, if the object, or the projection plane, is turned 30 degrees, the gear ratio of the train from the lower follower rack 25 to the pointer rack 35 is .500, and the ratio of the gear train from the upper follower rack 26 to the pointer rack 35 is .866.

Since producing special projections requires turning the object through various angles, means are provided to change these ratios. In the present embodiment of the invention said means are in the form of changeable gears. A set of gears for each degree from 5 to 45, inclusive may be provided, and answer the usual requirement. It should be noted that exact values of sines and cosines for some angles are expressed by decimalfractions having as many as five digits and even For ordinary drafting and designing work such precision is not necessary and if attempted would require gears with very large number of teeth. Therefore the precision of these ratios may be limited to desired accuracy.

FIG. 1 illustrate operation of the device for producing a special projection of an object. In the illustrated example the object has a form resembling that of a motor vehicle engine hood. For the purposes of clarity of description, said object will hereinafter be referred to as the hood. The numeral 50 designates an elevational view and the numeral 51 designates the top view of the hood resting on a horizontal surface. Presume now, that it is required to produce a top view of the hood turned 20 degrees around an axis projecting in views 50 and 51 as lines parallel to the base line of the drawing. In accordance with the conventional practice, it will be necessary to produce an end view, say at the left of the view 50 plotting each point of such View point-by-point by laying off the distances taken from the view 51, on the lines projected from the view 50. Thereupon, using a compass, arcs have to be drawn from each of the selected points and 20 degree angles be laid off on said are to determine the respective locations of the points moved on such arcs through said angle. Thereupon, the newly located points are projected upwardly on a line forming a 45 angle with the base line and pointing to the right,

and the points of intersection of the projecting lines with the 45 line are again projected by horizontal lines to the right. Thereupon, the corresponding points of the views 50 or 51 are projected upwardly to intersection with said horizontal lines to locate at their respective intersections points of the degree view. Connecting the newly located points with a smooth line will produce the end view of the hood turned 20 degrees.

All such tedious and time consuming operations requiring skill and close attention, and in addition providing possibilities of mistakes, are eliminated by the use of my improved device. Construction of intermediate or auxiliary view is also made unnecessary, and plotting of the points of the special projections is made directly from the two views, the elevation and the top view in the example illustrated.

To start the operations, the device is moved to the views 50 and 51, and the followers are set on the projections therein of some starting point. Starting with the near left hand corner of the hood, which in the view 50 is represented by the point 70a and in the view 51 by the point 70b, the follower 27 is and the device are moved to have the center of the locating point 29 fall on or coincide with the point 70a. The follower 30 is then moved to have the center of its locating hole 31 coincide with the point 70b in view 51. Because of such operations, the pointer 36 will be brought into a certain starting position at a point which is marked with a pencil as point 70c to represent the corner of the hood in the special projection view to be constructed. To locate the point representing in said special view the far left hand corner of the hood, appearing in the view as point 71a (and coinciding therein with point a), the follower 27 is placed at said point 71a, i.e. is left in place, and the follower 30 is moved up and placed at the point 71b in view 51. This will cause the pointer 36 to move up and stop at a location where marking a point through its marking hole gives position of the point 71c-i.e. location of the far left hand corner of the hood in the special projection view. The same procedure is used to find the rest of the points of the special projection view.

To give one more example, finding in said special view the location of the middle right hand point of the hood represented by point 72a in the view 50 and by point 72b in the view 51, the device is moved to the right and the follower 27 brought to the point 72a. The follower 30 is then moved to the point 7 2b, which movements bring the pointer 36 in the position to mark location of the point 72c in the special projection view. After sufficient number of points is thus plotted in the special projection view, they are connected by smooth lines thus providing a proper view.

The driving connections referred to above are of a positive nature and are preferably in the form of gear trains, as mentioned above. It is desired that when one of the connections is in operation, the other is made ineffective. This may be attained with the aid of various means such as frictional looks or clutches provided in each train and enabling the operator selectively to release one train for operation and keeping the other frictionally locked. However, I prefer to interpose in the driving connection a differential device which serves as a driving element and enables simultaneous movement of both followers and simultaneous operation of both trains.

The trains used in the present embodiment are best illustrated in FIGS. 5 and 8. FIG. 5 illustrates the gear train interposed between the follower rack 25 and the pointer rack 35. Referring to said figure, the rack 25 meshes with the gear which is secured to the hollow shaft 81 having a gear 82 mounted thereon and selectively friction-locked to its shoulders 83 by a knurled screw collar 84. The hollow shaft 81 and the gears connected thereto are free to rotate on the solid central pivot 85 fixed at its lower end to the bottom of the channel frame member 20 with the aid of a fiat nut 86.

The gear 82 meshes with a gear 87 which is mounted and selectively friction-locked with the aid of a knurled threaded collar 88 to the hollow extension 89 of a differential bevel gear 90. The gear 90 drives the differential spider 91. The spider 91 being in mesh with the second differential gear 92 may remain stationary, runs on said gear 92 and drives a sleeve 97 to which there is secured a gear 94 meshing with the pointer rack 35. Central pivot 98 secured to the bottom of the channel keeps the assembly in place.

The driving connection between the upper follower rack 26 with the pointer rack 35 is illustrated in FIG. 8. As shown therein, said rack 26 meshes with a gear 95 which is friction locked with the aid of threaded knurled collar 96 to the gear 73 which meshes with the gear 74. Said gear 74 is friction locked to the extension 93 of the second differential gear 92, see FIG. 5, and therefore it drives said gear 92 and through it the spider 91 which is secured to the sleeve 97 on which there is mounted the gear 94, as mentioned. Said gear 94 is in direct mesh with the pointer rack 35. The first differential gear 90 may remain stationary.

In the above description it was presumed that only one of the differential gears 90 and 92 was rotating at the same time, and therefore only one of the trains was operative at one time with the other remaining stationary. It will be understood, however, that the differential device described above permits simultaneous operation of both trains with the resultant movements of the pointer being in proportion so the gear ratios of the both trains and without affecting correctness of the resultant position to which the pointer arrives.

It will also be understood that provision of the differential device decreases the gear ratios of the trains dividing such ratios by 2. Therefore, the trains of the device including a differential are twice those used in a device using separate clutches or similar means locking one of the trains for operation of the other.

For the purposes of changing gear ratios of the trains when the object is turned through different angle than that for which the machine is adapted, the gears that are changed are represented in the present embodiment by the gears 82 and 87, see FIG. 5, and the gears 73 and 74, see FIG. 8. Also in order to provide for changes in the distances between the central pivot slots 99 and 100 are provided in the bottom of the channel 20.

It will be now seen in view of the foregoing that my improved device operates as a combined computer, a measuring device, and a distance-laying-off device, and thus performs in a simple movement all such operations.

It will also be understood that while the: vertical arrangem'ent of the device has the advantage of utilizing its weight to improve its stability in operation, and eliminate the effect of the back lash in the gear teeth, the device may be used extending horizontally and be provided for such purposes with a T-Square head.

I claim:

1. In a projecting and plotting device, two followers and one pointer, a separate driving connection between each of said followers and said pointer, with said pointer and said followers movable along the same straight line, with said pointer moving in response to the movement of one of said followers through a distance equal to that of the follower multiplied by the sine of a predetermined angle, with the driving connection of the pointer to the other follower being inoperative in the process of such movement, with said pointer moving in response to the movement of the second follower through a distance equal to that of the second follower multiplied by the cosine of the same angle, with the driving connection between the pointer and the first follower being inoperative in the process of said last movement.

2. The device defined in claim 1, with the driving connections between the followers and the pointer being in the form of gear trains.

3. The device defined in claim 1, with the driving connections between the followers and the pointer being in the form of gear trains, and clutches provided in each of said trains to selectively connect and disconnect the same.

4. In a projecting and plotting device, an elongated frame member, means adapting said frame member to be moved along a drawing retaining constant angular relationship with the base line thereof, two gear racks operatively mounted on said frame member for straight line movements therein, two followers mounted on said racks, each follower movable with its respective rack along a common straight line path, a third rack operatively mounted on said frame member and having a point er movable therewith along a line parallel to the line of movements of said followers, and a gear train between each of said follower racks and said pointer rack.

5. The invention defined in claim 4, the gear trains having gear ratios corresponding respectively to predetermined trigonometric functions of the same predetermined angle.

, 6. The invention defined in claim 4, the gear trains having ratios corresponding respectively to the sine and the cosine of the same predetermined angle.

77 The invention defined in claim 4, the'gear trains having ratios corresponding respectively to the sine and the cosine of the same predetermined angle, said gear trains including replaceable gears to vary said ratios.

8. The device defined in claim 1, with the driving connections between the followers and the pointer being in the form of gear trains, and a differential device connected to each of said train to produce simultaneous operativeness of the respective trains.

References Cited by the Examiner UNITED STATES PATENTS 2,557,944 6/1951 Crook 33-23 X 2,711,024 6/1955 Sachtleber 3377 2,714,253 8/1955 Stone 33-18 2,770,046 11/ 1956 Wichmann 33-192 LEONARD FORMAN, Primary Examiner.

ISAAC LISANN, Examiner.

HARRY N. HAROIAN, Assistant Examiner. 

1. IN A PROJECTING AND PLOTTING DEVICE, TWO FOLLOWERS AND ONE POINTER, A SEPARATE DRIVING CONNECTION BETWEEN EACH OF SAID FOLLOWERS AND SAID POINTER, WITH SAID POINTER AND SAID FOLLOWERS MOVABLE ALONG THE SAME STRAIGHT LINE, WITH SAID POINTER MOVING IN RESPONSE TO THE MOVEMENT OF ONE OF SAID FOLLOWERS THROUGH A DISTANCE EQUAL TO THAT OF THE FOLLOWER MULTIPLIED BY THE SINE OF A PREDETERMINED ANGLE, WITH THE DRIVING CONNECTION OF THE POINTER TO THE OTHER FOLLOWER BEING INOPERATIVE IN THE PROCESS OF SUCH MOVEMENT, WITH SAID POINTER MOVING IN RESPONSE TO THE MOVEMENT OF THE SECOND FOLLOWER THROUGH A DISTANCE EQUAL TO THAT OF THE SECOND FOLLOWER MULTIPLIED BY THE COSINE OF THE SAME ANGLE, WITH THE DRIVING CONNECTION BETWEEN THE POINTER AND THE FIRST FOLLOWER BEING INOPERATIVE IN THE PROCESS OF SAID LAST MOVEMENT. 